Abstract

Due to the need for a non-destructive method to measuresound absorption of acoustic materials,in situ methods have achieved significance in research on acoustic. So, the goal of this work is to build and test a system of in situmeasurement of acoustic impedance to be used as an academic tool for undergraduate students of Acoustical Engineering on the Federal University of Santa Maria, Brazil. At first, two measurement techniques are introduced in this article: PP system and PU probe. Then, numerical analyses through a FEM model for both techniques are presented. The choice of FEM to model the measurement system occurs as an alternative to the BEMmodel, widely used in the literature. Thus, through the numerical model, errors were observed due to the finite size of sample. So, a strategy based on techniques proposed by the literature was applied, obtaining better precision. All numerical analysis were referenced on the Johnson-Champoux-Allard model of porous material. At last, a prototype of the measurement system is presented, followed by experimental results, using two microphones (PP system). There results were compared to measurement performed with an Impedance Tube.